Estimating JUNO’s Sensitivity to Solar Neutrino-to-antineutrino Conversion and Neutrino Magnetic Moments

Abstract We investigated JUNO’s sensitivity to a possible conversion of solar neutrinos into antineutrinos via the spin-flavor precession mechanism, and assessed the implications for constraining the neutrino-magnetic moment. Using a sensitivity-based framework appropriate for counting experiments with no prior observations, we derive 90% confidence level ensemble-average sensitivities on the solar antineutrino flux for 1.8–16.8 and 8.0–16.8 MeV. For the entire energy window, the results do not improve the restrictions of other experiments; the relevance occurs in the highest-energy window. In this window, we report a flux of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">lim</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:mn>4.01</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> and a probability of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>→</mml:mo> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mo>≤</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>2.07</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msup> </mml:math> , the latter normalized to the 8 B flux above threshold, Φ SSM ( E &gt; 8 MeV). Assuming transverse solar magnetic fields of B ⊥ = 50 and 100 kG, the corresponding magnetic-moment sensitivities are μ ν ≤ 7.27 × 10 −11 μ B and 3.64 × 10 −11 μ B in the high-energy window. These results highlight that JUNO has the potential to achieve sensitivities comparable to the most stringent astrophysical limits; in particular, the high-energy selection (8.0–16.8 MeV) provides a sensitivity that is competitive with current results, while the full-energy window remains primarily limited by near-reactor backgrounds.